1. Field Of The Invention
The invention relates to closed hot water heating systems or pressurized water systems, and more particularly to an expansion tank, forming part of the system, and the construction thereof. Stated otherwise, the invention relates to expansion tanks and, more particularly, to improved expansion tanks adapted to form part of a hot water heating system or a pressurized water system.
2. Prior Art
Water contains air in the absorbed state in nearly inverse proportion to its temperature. This air is liberated into the system when the water is heated and accumulates in the compression tank and other portions of the heating system. A reduction in heating efficiency results, making continuous venting of radiators or convectors necessary. The water as it is heated expands and moves into the compression tank which is connected to the piping through which the water is circulated. When the temperature of the boiler water reaches the desired degree, the firing of the boiler ceases. The water begins to cool and contract. As it cools, that part of the boiler water in direct contact with air in the compression tank absorbs some of the air in the tank. Through thermal circulation this aircharged water in the compression tank is changed continually so that in the next heating cycle this re-absorbed air is liberated into the system. This reversible process is repeated as often as the firing cycle is repeated and the boiler water is heated and cooled. As a result of this process the pressure in the system varies considerably and eventually the system may cease to function.
Expansion tanks in domestic water systems provide an air cushion for the supply water. The air and water in early systems were in direct contact. Air being soluble in water, the water absorbs air. The water in the system might eventually absorb the air cushion in the expansion tanks, leaving a static water system which necessitates the constant operation of a pressure pump. Subsequently an air surge chamber was provided which was not in direct contact with the water, thereby eliminating the need of the pressure pump operating every time a faucet was turned on.
U.S. Pat. No. 3,035,614 discloses expansion tanks which include a pair of hollow body members, each of which have an end and a tubular skirt portion. The skirt portions are united in end-to-end relation to form a tank. There is a flexible diaphragm in and spanning the tank and having a peripheral portion in peripheral engagement with the skirt of one of the body members. A continuous retaining ring engages the peripheral portion and retains it in engagement with the skirt of the body member. There is a groove in the exterior of the ring and a substantially complemental corrugation in the skirt of the body member compressing the peripheral portion into the groove to secure the diaphragm against movement endwise of the tank and seal the diaphragm to the skirt. See also U.S. Pat. No. 2,695,753.
U.S. Pat. No. 3,524,475 discloses expansion tanks which include a hollow body having a side wall and end walls and a liquid-impervious liner having an end wall and a side wall covering the corresponding end wall and a portion of the side wall of the body in adjacent non-adhering relation thereto. The liner has a peripheral edge portion contacting the side wall. There is a flexible diaphragm dividing the interior of the body into two sections. One of the sections is adapted to receive a liquid. The diaphragm has a peripheral portion disposed in overlying relation to the peripheral edge portion of the liner. There is also means retaining the peripheral portions of the diaphragm and the liner against the side wall to form a liquid-tight seal between the peripheral portions of the diaphragm and the liner. The retaining means includes a continuous ring engaging and receiving the peripheral portion of the diaphragm. The side wall engages the peripheral edge portion of the liner. The ring and wall have a complemental rib and groove securing the diaphragm to the side wall. The diaphragm is formed with a bead on its peripheral portion, with the bead being received between the rib and the groove.